1. Field of the Invention
This invention relates to endoscopic surgical instruments. More particularly, the present invention relates to double acting endoscopic scissors having bipolar cautery capability and to an endoscopic instrument handle with a non-bonded, non-welded ferrule which facilitates a rotating of the tube, clevis, and end effectors relative to the handle.
2. State of the Art
Endoscopic surgery is widely practiced throughout the world today and its acceptance is growing rapidly. In general, endoscopic surgery involves one or more incisions made by trocars where trocar tubes are left in place so that endoscopic surgical instruments may be inserted through the tubes. A camera or magnifying lens is often inserted through one trocar tube, while a cutter, dissector, or other surgical instrument is inserted through another trocar tube for purposes of manipulating and/or cutting the internal organ. Sometimes it is desirable to have several trocar tubes in place at once in order to receive several surgical instruments. In this manner, organs or tissue may be grasped with one surgical instrument, and simultaneously may be cut with another surgical instrument; all under view of the surgeon via the camera.
By 1996, it is expected that more than two million additional endosurgeries will be performed per year that, in 1990, were done via open surgery (MedPRO Month, I:12, p.178). The advantages of endoscopic surgery are clear in that it is less invasive, less traumatic and recovery is typically quicker. As a result, many new instruments and devices for use in endosurgery are introduced every year.
Endoscopic surgical instruments generally include a tube, a push rod which extends through the tube, an actuating means engaging the tube and the push rod for imparting reciprocal axial motion to the push rod, end effector means (typically two end effectors) coupled to the push rod by linkage means, and a clevis coupled to the tube at its proximal end and to the end effector means at its distal end, wherein axial movement of the push rod effects movement of the end effector means in a plane parallel to the longitudinal axis of the push rod. For purposes herein, the "distal end" of a surgical instrument or any part thereof, is the end most distant from the surgeon and closest to the surgical site, while the "proximal end" of the instrument or any part thereof, is the end most proximate the surgeon and farthest from the surgical site. The end effectors may be grippers, cutters, forceps, scissors, etc.
Endoscopic instruments may be generally classified as either "single acting" or "double acting". In a single acting instrument, a stationary end effector is coupled to the distal end of the tube and a movable end effector is coupled to the distal end of the push rod and is mounted for rotation relative to the stationary end effector. In single acting instruments, a clevis is not required. It is only necessary to provide a rotational coupling between the stationary end effector and the movable end effector. In double acting instruments, two end effectors are mounted for rotation in a clevis which is coupled to the distal end of the tube; and both end effectors are coupled to the distal end of the push rod.
Many endoscopic instruments are provided with cautery capability. Endoscopic cautery instruments may be monopolar or bipolar. In monopolar instruments, both end effectors are electrically coupled to a single pole of a source of cautery current. RF energy is conducted from the end effectors through the patient's body to a remote "body plate". In bipolar instruments, each end effector is coupled to a separate pole of a source of cautery current. RF energy is conducted from one end effector through the patient's body to the other end effector. Monopolar instruments suffer from the fact that the return path between the end effectors and the large area body plated can be unpredictable as the electrical current seeks the path of least resistance. With bipolar instruments, however, the path of the current is very short, from one end effector to the other, and involves only the tissue and fluids in the short path between the electrodes. However, bipolar endoscopic instruments are difficult to manufacture. The end effectors must be electrically insulated from each other and some means must be found to provide a separate electrical connection to each end effector. These problems are most acute in the construction of endoscopic scissors which have blades in virtually constant contact with each other.
European Patent Number 0 572 131 A1 to Rydell discloses surgical scissors with a bipolar coagulation feature. Rydell's scissors are single acting. A first scissor blade is mounted on the distal end of a hollow tube and a second blade is pivotally mounted to the first scissor blade. A rigid conductive wire or rod is coupled to the second scissor blade and extends through the hollow tube. The blades are constructed of metal blanks with bonded ceramic insulators insulating the blades from each other along their entire lengths. An insulating pivot member pivotally couples the second blade to the first blade. The rigid rod is covered with an insulating material. Scissor handles are coupled to the proximal ends of the tube and the rod. A first lead wire is coupled to the proximal end of the rod and a second lead wire is coupled to the interior of the hollow tube by means of a copper wave spring entering the proximal end of the tube. As mentioned above, the scissors are single acting, one blade moves as the other remains stationary. The movable blade is pivotally coupled to the stationary blade by a non-conductive screw which enters a threaded opening in the stationary blade or by a conductive screw which enters an insulated threaded opening in the stationary blade.
Rydell's scissors are difficult to manufacture. The blades must be made of ceramic bonded metal blanks. The electrical and mechanical couplings are complex and intricate. Providing threads in the stationary blade requires that it be relatively thick and weakens the construction considerably. Rydell's scissors do not present a workable solution to the problems of bipolar scissors. Additionally, Rydell's design is limited in other ways in that the scissors are not double acting and the blades cannot be rotated relative to the longitudinal axis of the tube.
European Patent Number 0 518 230 A1 to Eggers discloses bipolar electrosurgical endoscopic instruments including double acting bipolar endoscopic scissors. Eggers' scissors have an actuating handle coupled to the proximal ends of a tube and push rod and a pair of double acting scissor blades coupled to the end of the tube. The distal end of the push rod is coupled to the scissor blades for rotating them relative to each other. The tube and the push rod are rotationally mounted in the handle so that the tube and the push rod are rotatable about the longitudinal axis of the tube. Eggers achieves a bipolar coupling through the push rod alone. Eggers' push rod is a composite of two semicylindrical halves bonded to each other with an insulating layer between them. The insulating layer also covers the outer surface of the push rod to insulate it from the inner surface of the tube. The distal end of the push rod is slotted so as to provide a bipolar fork, each tine being the distal end of one semicylindrical half of the push rod. Facing surfaces of the tines are not insulated and provide the electrical contact surfaces for electrical coupling with the scissor blades. The distal end of the tube has a similar slot for mounting the scissor blades. The scissor blades each have a pivot hole and a slotted shank portion and at least one of the blades is coated with electrical insulation on the surface which faces the other blade. The outer surfaces of the shank portions are not insulated. The scissor blades are mounted on a non-conductive pivot pin which engages a hole transverse to the slot in the distal end of the tube. The slotted shank portions of the blades enter the space between the tines of the push rod and are coupled to the push rod by a nonconductive pivot pin which enters the slots of the shanks and engages a hole in each tine. Movement of the push rod relative to the tube moves the pivot pin in the slots of the shanks of the blades and causes them to rotate about the pivot pin in the tube. The outer surfaces of the slotted shanks rub against the inner surfaces of the tines and make electrical contact therewith. The inner surface of at least one shank is coated to insulate it from the other shank.
Eggers' bipolar scissors present interesting ideas, but they also are difficult to manufacture and are unlikely to be functional. The construction of the bipolar push rod is complicated. The electrical connection between the push rod and the scissor blades is dependent on a good frictional engagement between the tines of the push rod and the shanks of the scissor blades and can weaken over time. In addition, the number of pivot pins and insulators is excessive, thereby making the assembly of the distal end of the device intricate.
It is well known to provide an endoscopic instrument handle with a ferrule for rotating the tube and clevis (and thus the end effectors) relative to the handle. Some of these ferrules usually include biasing springs and locking mechanisms so that the tube does not freely rotate out of a selected position. These locking ferrule arrangements require the practitioner to slide the ferrule against a biasing spring while rotating the tube of the instrument. In addition, many commonly used ferrules are either welded or otherwise bonded to the hollow tube of the endoscopic instrument. In order to allow rotation of the hollow tube relative to the handle, a certain amount of axial play is permitted between the handle and the tube. This axial play results in what is known as "slop" i.e. undesired movement of the tube in response to movement of the actuator lever in the handle. Slop decreases the responsiveness of the end effectors. Also, in the case of cautery instruments, it is important that the ferrule coupling be non-conductive.